Basalt

Basalt is a dark volcanic rock that has been pushed to the surface after eons of molten rock being pushed towards the surface!

Generation
Basalt can generate anywhere in the world above y=30, all the way up to the surface layers. Its dark color make it stand out prominently from the other types of stone and it can spawn in vast quantities.

Decoration
Like many of the earthly materials in the world, they can be crafted into various different blocks for building and decoration. Interestingly, Basalt is the only new block type added that has a Cobblestone variant. In lieu of Silk Touch, you'll have to pop the Basalt Cobblestone into a furnace like you would have to with regular Cobblestone. Putting Vines or Willows together with Basalt items will turn them mossy.